Re: [PATCH perf/core] perf intel-pt: Fix clang build failure in intel_pt_synth_pebs_sample

Ian Rogers
2020-05-14T00:56:20Z

On Wed, May 13, 2020 at 4:43 PM Gustavo A. R. Silva
<gustavoars@kernel.org> wrote:
>
> Fix the following build failure generated with command
> $ make CC=clang HOSTCC=clang -C tools/ perf:
>
> util/intel-pt.c:1802:24: error: field 'br_stack' with variable sized type 'struct branch_stack' not at the end of a struct or class is a GNU extension [-Werror,-Wgnu-variable-sized-type-not-at-end]
> struct branch_stack br_stack;
> ^
> 1 error generated.
>
> Fix this by reordering the members of struct br.
>
> Clang version 11.0.0 was used.
>
> Fixes: f283f293a60d ("perf tools: Replace zero-length array with flexible-array")
> Reported-by: Ian Rogers <irogers@google.com>
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Tested-by: Ian Rogers <irogers@google.com>

Thanks!
Ian

> ---
> Here to fix what I break. :)
>
> tools/perf/util/intel-pt.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
> index f17b1e769ae4..b34179e3926f 100644
> --- a/tools/perf/util/intel-pt.c
> +++ b/tools/perf/util/intel-pt.c
> @@ -1799,8 +1799,8 @@ static int intel_pt_synth_pebs_sample(struct intel_pt_queue *ptq)
>
> if (sample_type & PERF_SAMPLE_BRANCH_STACK) {
> struct {
> - struct branch_stack br_stack;
> struct branch_entry entries[LBRS_MAX];
> + struct branch_stack br_stack;
> } br;
>
> if (items->mask[INTEL_PT_LBR_0_POS] ||
> --
> 2.26.2
>